This proposal deals with a study of the mechanism of biosynthesis of beta-lactam antibiotics. In particular, an active cell extract of Cephalosporium acremonium has now been prepared, which catalyzed the conversion of delta-(alpha-L-aminoadipyl)-L-cysteinly-D-(alpha-H3)-valine into H3-penicillin N. We are now in the process of improving the yield of this conversion and defining the coenzyme requirements. The synthesis of delta-(alpha-D-aminoadipyl)-L-cysteinyl-D-(alpha-H3)-valine and delta-(alpha-L-aminoadipyl)-L-cysteinyl-D-(alpha-H3)-beta-hydroxyvaline is currently in progress. BIBLIOGRAPHIC REFERENCES: F. C. Huang, J. A. Chan, C. J. Sih, P. Fawcett and E. P. Abraham, The non-participation of alpha, beta-dehydrovalinyl intermediates in the formation of L-delta(alpha-aminoadipyl)-L-cysteinyl-D-valine. J. Amer. Chem. Soc., 97, 3858 (1975). J. A. Chan, F. C. Huang and C. J. Sih, The absolute configuration of the amino acids in delta(alpha-aminoadipyl)cysteinylvaline from Penicillium chrysogenum. Biochemistry, 15, 177 (1976).